This invention relates to an aluminosilicate zeolite having the BPH topology and designated UZM-4. The UZM-4 composition is structurally related to zeolite Q, but is thermally stable up to a temperature of 600xc2x0 C. and has higher Si/Al ratios in the range of about 1.5 to about 4.0.
Zeolites are crystalline aluminosilicate compositions which are microporous and which are formed from corner sharing AlO2 and SiO2 tetrahedra. Numerous zeolites, both naturally occurring and synthetically prepared are used in various industrial processes. Zeolites are characterized by having pore openings of uniform dimensions, having a significant ion exchange capacity, and being capable of reversibly desorbing an adsorbed phase which is dispersed throughout the internal voids of the crystal without significantly displacing any atoms which make up the permanent zeolite crystal structure.
One particular zeolite, designated zeolite Q, was first disclosed in U.S. Pat. No. 2,991,151. The general formula for zeolite Q is represented in terms of mole ratio of the oxides by the following:
0.95xc2x10.05 M2/nO:Al2O3:2.2xc2x10.05 SiO2:xH2O
where M designates at least one exchangeable cation, n represents the valence of M and x has a value from 0 to about 5. The examples in the patent are prepared with M being potassium. Synthesis of zeolite Q was conducted at 25xc2x0 C. to 50xc2x0 C. After activation at about 130xc2x0 C., zeolite Q was found to adsorb small polar molecules.
In a paper by John D. Sherman entitled, xe2x80x9cIdentification and Characterization of Zeolites Synthesized in the K2Oxe2x80x94Al2O3xe2x80x94SiO2xe2x80x94H2O System,xe2x80x9d Molecular Sievesxe2x80x94II(102) 30, 1974, he reports that the zeolite Q of the ""151 patent is the same zeolite as zeolite K-I reported by other researchers. Zeolite K-I was first reported by S. P. Zhdanov and M. E. Ovsepyon in Doklady Chemistry. Proc. Acad. Sci. USSR, 156, 756 (1964). M. E. Ovsepyan and S. P. Zhdanov further reported on K-I zeolite in Bull. Acad. Sci. USSR, Chem. Sci. 1, 8 (1965). R. M. Barrer et al. in J. Chem. Soc. (A) 2475 (1968) showed that K-I decomposed at 168xc2x0 C. It is also reported by Sherman and other researchers that zeolite Q is unstable above 130xc2x0 C. and is totally disintegrated at 200xc2x0 C. Owing to this thermal instability, zeolite Q has received little industrial interest. K. J. Andries et al., in Zeolites, 11, 124 (1991) proposed the BPH topology for zeolite Q. Synthesis of a pure form of zeolite Q was reported by K.J. Andries et al., in Zeolites, 11, 116 (1991). Finally, U.S. Pat. No. 5,382,420 discloses a composition designated ECR-33, which is a partially rare earth (La) exchanged zeolite Q. In all of the above reports, the Si/Al ratio is 1.
Applicants have now synthesized a zeolite designated UZM-4, which appears to have a similar topology to that of zeolite Q, i.e., BPH, but has considerably different characteristics. The biggest difference is that UZM-4 has been synthesized with higher Si/Al ratios than zeolite Q, starting from a low of about 1.5 and going higher. The most important characteristic of UZM-4 is the greater thermal stability associated with the higher Si/Al ratios. UZM-4 in its various forms is stable to at least 400xc2x0 C. and often up to greater than 600xc2x0 C. The x-ray diffraction pattern of UZM-4 is noticeably different from that of zeolite-Q; and UZM-4 has smaller cell dimensions than that of zeolite Q, consistent with its higher Si/Al ratio.
As stated, the present invention relates to a new aluminosilicate zeolite designated UZM-4. Accordingly, one embodiment of the invention is a microporous crystalline zeolite having a three-dimensional framework of at least AlO2 and SiO2 tetrahedral units and an empirical composition on an as synthesized and anhydrous basis expressed by an empirical formula of:
Mmn+Rrp+Al1xe2x88x92xExSiyOz
where M is at least one exchangeable cation selected from the group consisting of alkali and alkaline earth metals, xe2x80x9cmxe2x80x9d is the mole ratio of M to (Al+E) and varies from about 0.05 to about 0.95, R is at least one organic cation selected from the group consisting of protonated amines, protonated diamines, quaternary ammonium ions, diquaternary ammonium ions, protonated alkanolamines, and quaternized alkanolammonium ions, xe2x80x9crxe2x80x9d is the mole ratio of R to (Al+E) and has a value of about 0.05 to about 0.95, xe2x80x9cnxe2x80x9d is the weighted average valence of M and has a value of about 1 to about 2, xe2x80x9cpxe2x80x9d is the weighted average valence of R and has a value of about 1 to about 2, E is an element selected from the group consisting of gallium, iron, boron, chromium, indium and mixtures thereof, xe2x80x9cxxe2x80x9d is the mole fraction of E and has a value from 0 to about 0.5, xe2x80x9cyxe2x80x9d is the mole ratio of Si to (Al+E) and varies from about 1.5 to about 4 and xe2x80x9czxe2x80x9d is the mole ratio of O to (Al+E) and has a value determined by the equation:
z=(mxc2x7n+rxc2x7p+3+4xc2x7y)/2
and is characterized in that it has the x-ray diffraction pattern having the d spacings and intensities set forth in Table A:
and is thermally stable up to a temperature of about 400xc2x0 C.
Another embodiment of the invention is a process for preparing the crystalline microporous zeolite described above. The process comprises forming a reaction mixture containing reactive sources of M, R, Al, Si and optionally E at a temperature of about 85xc2x0 C. to about 225xc2x0 C., the reaction mixture having a composition expressed in terms of mole ratios of the oxides of:
aM2/nO:bR2/pO:1-cAl2O3:cE2O3:dSiO2:eH2O
where xe2x80x9caxe2x80x9d has a value of about 0.05 to about 1.5, xe2x80x9cbxe2x80x9d has a value of about 1.0 to about 15, xe2x80x9ccxe2x80x9d has a value of 0 to about 0.5, xe2x80x9cdxe2x80x9d has a value of about 2.5 to about 15, xe2x80x9cexe2x80x9d has a value of about 25 to about 2500.
Yet another embodiment of the invention is a hydrocarbon conversion process using the above-described zeolite. The process comprises contacting the hydrocarbon with the zeolite at conversion conditions to give a hydroconverted hydrocarbon.
Applicants have prepared an aluminosilicate zeolite and substituted versions of the same whose topological structure is related to BPH as described in Atlas of Zeolite Structure Types, W. H. Meier, D. H. Olson, and C.H. Baerlocher, editors, Elsevier, (1996), 68-69, which has been designated UZM-4. As will be shown in detail, UZM-4 is different from zeolite Q in a number of its characteristics. The instant microporous crystalline zeolite (UZM-4) has an empirical composition in the as-synthesized form and on an anhydrous basis expressed by the empirical formula:
Mmn+Rrp+Al1xe2x88x92xExSiyOz
where M is at least one exchangeable cation and is selected from the group consisting of alkali and alkaline earth metals. Specific examples of the M cations include but are not limited to lithium, sodium, potassium, rubidium, cesium, calcium, strontium, barium and mixtures thereof. R is an organic cation and is selected from the group consisting of protonated amines, protonated diamines, quaternary ammonium ions, diquaternary ammonium ions, protonated alkanolamines and quaternized alkanolammonium ions. The value of xe2x80x9cnxe2x80x9d which is the weighted average valence of M varies from about 1 to about 2. The value of xe2x80x9cpxe2x80x9d which is the weighted average valence of R varies from 1 to about 2. The ratio of silicon to (Al+E) is represented by xe2x80x9cyxe2x80x9d which varies from about 1.5 to about 4.0. E is an element which is tetrahedrally coordinated, is present in the framework and is selected from the group consisting of gallium, iron, chromium, indium and boron. The mole fraction of E is represented by xe2x80x9cxxe2x80x9d and has a value from 0 to about 0.5, while xe2x80x9czxe2x80x9d is the mole ratio of 0 to (Al+E) and is given by the equation
z=(mxc2x7n+rxc2x7p+3+4xc2x7y)/2
Where M is only one metal, then the weighted average valence is the valence of that one metal, i.e. +1 or +2. However, when more than one M metal is present, the total amount of
Mmn+=Mm1(n1)++Mm2(n2)++Mm3(n3)++ . . . 
and the weighted average valence xe2x80x9cnxe2x80x9d is given by the equation:   n  =                              m          1                ·                  n          1                    +                        m          2                ·                  n          2                    +                        m          3                ·                  n          3                    +      ⋯                      m        1            +              m        2            +                        m          3                ⁢                  xe2x80x83                ⁢        ⋯            
Similarly when only one R organic cation is present, the weighted average valence is the valence of the single R cation, i.e., +1 or +2. When more than one R cation is present, the total amount of R is given by the equation.
ti Rrp+=Rr1(p1)++Rr2(p2)++Rr3(p3)+
and the weighted average valence xe2x80x9cpxe2x80x9d is given by the equation   p  =                              p          1                ·                  r          1                    +                        p          2                ·                  r          2                    +                        p          3                ·                  r          3                    +      ⋯                      r        1            +              r        2            +              r        3            +      ⋯      
The microporous crystalline zeolite, UZM-4, is prepared by a hydrothermal crystallization of a reaction mixture prepared by combining reactive sources of M, R, aluminum, silicon and optionally E. The sources of aluminum include but are not limited to aluminum alkoxides, precipitated aluminas, aluminum metal, aluminum salts and alumina sols. Specific examples of aluminum alkoxides include, but are not limited to aluminum ortho sec-butoxide and aluminum ortho isopropoxide. Sources of silica include but are not limited to tetraethylorthosilicate, colloidal silica, precipitated silica and alkali silicates. Sources of the E elements include but are not limited to alkali borates, boric acid, precipitated gallium oxyhydroxide, gallium sulfate, ferric sulfate, ferric chloride, chromium nitrate and indium chloride. Sources of the M metals include the halide salts, nitrate salts, acetate salts, and hydroxides of the respective alkali or alkaline earth metals. When R is a quaternary ammonium cation or a quaternized alkanolammonium cation, the sources include the hydroxide, chloride, bromide, iodide and fluoride compounds. Specific examples include without limitation tetramethylammonium hydroxide, tetraethylammonium hydroxide, hexamethonium bromide, diethyldimethylammonium hydroxide, tetrapropylammonium hydroxide, tetramethylammonium chloride and choline chloride. R may also be introduced as an amine, diamine, or alkanolamine. Specific examples are N,N,Nxe2x80x2,Nxe2x80x2-tetramethyl -1,6-hexanediamine, triethylamine, and triethanolamine.
The reaction mixture containing reactive sources of the desired components can be described in terms of molar ratios of the oxides by the formula:
aM2/nO:bR2/pO:1-cAl2O3:cE2O3:dSiO2:eH2O
where xe2x80x9caxe2x80x9d varies from about 0.05 to about 1.5, xe2x80x9cbxe2x80x9d varies from about 1.0 to about 15, xe2x80x9ccxe2x80x9d varies from about 0 to 0.5, xe2x80x9cdxe2x80x9d varies from about 2.5 to about 15, and xe2x80x9cexe2x80x9d varies from about 25 to about 2500. If alkoxides are used, it is preferred to include a distillation or evaporative step to remove the alcohol hydrolysis products. The reaction mixture is now reacted at a temperature of about 85xc2x0 C. to about 225xc2x0 C. and preferably from about 125xc2x0 C. to about 150xc2x0 C. for a period of about 1 day to about 2 weeks and preferably for a time of about 2 days to about 4 days in a sealed reaction vessel under autogenous pressure. After crystallization is complete, the solid product is isolated from the heterogeneous mixture by means such as filtration or centrifugation, and then washed with deionized water and dried in air at ambient temperature up to about 100xc2x0 C.
The UZM-4 aluminosilicate zeolite, which is obtained from the above-described process, is characterized by the x-ray diffraction pattern, having the d-spacings and relative intensities set forth in Table A below.
As will be shown in detail in the examples, the UZM-4 material is thermally stable up to a temperature of at least 400xc2x0 C. and preferably up to about 600xc2x0 C. The UZM-4 material has also been found to have a smaller unit cell size than zeolite Q, indicative of a higher Si/Al ratio. That is, a representative UZM-4 has a unit cell of a=13.269 xc3x85, c=13.209 xc3x85, versus a unit cell for zeolite Q of a=13.501 xc3x85 and c=13.403 xc3x85.
As synthesized, the UZM-4 material will contain some of the exchangeable or charge balancing cations in its pores. These exchangeable cations can be exchanged for other cations, or in the case of organic cations, they can be removed by heating under controlled conditions. Because UZM-4 is a large pore zeolite, it is also possible to remove some organic cations directly by ion exchange.
The crystalline UZM-4 zeolite of this invention can be used for separating mixtures of molecular species, removing contaminants through ion exchange and catalyzing various hydrocarbon conversion processes. Separation of molecular species can be based either on the molecular size (kinetic diameter) or on the degree of polarity of the molecular species.
The UZM-4 zeolite of this invention can also be used as a catalyst or catalyst support in various hydrocarbon conversion processes. Hydrocarbon conversion processes are well known in the art and include cracking, hydrocracking, alkylation of both aromatics and isoparaffin, isomerization, polymerization, reforming, hydrogenation, dehydrogenation, transalkylation, dealkylation, hydration, dehydration, hydrotreating, hydrodenitrogenation, hydrodesulfurization, methanation and syngas shift process. Specific reaction conditions and the types of feeds which can be used in these processes are set forth in U.S. Pat. Nos. 4,310,440 and 4,440,871 which are incorporated by reference. Preferred hydrocarbon conversion processes are those in which hydrogen is a component such as hydrotreating or hydrofining, hydrogenation, hydrocracking, hydrodenitrogenation, hydrodesulfurization, etc.
Hydrocracking conditions typically include a temperature in the range of 400xc2x0 to 1200xc2x0 F. (204-649xc2x0 C.), preferably between 600xc2x0and 950xc2x0 F. (316-510xc2x0 C.). Reaction pressures are in the range of atmospheric to about 3,500 psig (24,132 kPa g), preferably between 200 and 3000 psig (1379-20,685 kPa g). Contact times usually correspond to liquid hourly space velocities (LHSV) in the range of about 0.1 hrxe2x88x921 to 15 hrxe2x88x921, preferably between about 0.2 and 3 hrxe2x88x921. Hydrogen circulation rates are in the range of 1,000 to 50,000 standard cubic feet (scf) per barrel of charge (178-8,888 std. m3/m3), preferably between 2,000 and 30,000 scf per barrel of charge (355-5,333 std. m3/m3). Suitable hydrotreating conditions are generally within the broad ranges of hydrocracking conditions set out above.
The reaction zone effluent is normally removed from the catalyst bed, subjected to partial condensation and vapor-liquid separation and then fractionated to recover the various components thereof. The hydrogen, and if desired some or all of the unconverted heavier materials, are recycled to the reactor. Alternatively, a two-stage flow may be employed with the unconverted material being passed into a second reactor. Catalysts of the subject invention may be used in just one stage of such a process or may be used in both reactor stages.
Catalytic cracking processes are preferably carried out with the UZM-4 composition using feedstocks such as gas oils, heavy naphthas, deasphalted crude oil residua, etc. with gasoline being the principal desired product. Temperature conditions of 850xc2x0 to 1100xc2x0 F., LHSV values of 0.5 to 10 and pressure conditions of from about 0 to 50 psig are suitable.
Alkylation of aromatics usually involves reacting an aromatic (C2 to C12), especially benzene, with a monoolefin to produce a linear alkyl substituted aromatic. The process is carried out at an aromatic: olefin (e.g., benzene:olefin) ratio of between 5:1 and 30:1, a LHSV of about 0.3 to about 6 hrxe2x88x921, a temperature of about 100xc2x0 to about 250xc2x0 C. and pressures of about 200 to about 1000 psig. Further details on apparatus may be found in U.S. Pat. No. 4,870,222 which is incorporated by reference.
Alkylation of isoparaffins with olefins to produce alkylates suitable as motor fuel components is carried out at temperatures of xe2x88x9230xc2x0 to 40xc2x0 C., pressures from about atmospheric to about 6,894 kPa (1,000 psig) and a weight hourly space velocity (WHSV) of 0.1 to about 120. Details on paraffin alkylation may be found in U.S. Pat. Nos. 5,157,196 and 5,157,197, which are incorporated by reference.
The following examples are presented in illustration of this invention and are not intended as undue limitations on the generally broad scope of the invention as set out in the appended claims.
The structure of the UZM-4 zeolite of this invention was determined by x-ray analysis. The x-ray patterns presented in the following examples were obtained using standard x-ray powder diffraction techniques. The radiation source was a high-intensity, x-ray tube operated at 45 kV and 35 ma. The diffraction pattern from the copper K-alpha radiation was obtained by appropriate computer based techniques. Flat compressed powder samples were continuously scanned at 2xc2x0 to 70xc2x0 (2xcex8). Interplanar spacings (d) in Angstrom units were obtained from the position of the diffraction peaks expressed as xcex8 where xcex8 is the Bragg angle as observed from digitized data. Intensities were determined from the integrated area of diffraction peaks after subtracting background, xe2x80x9coxe2x80x9d being the intensity of the strongest line or peak, and xe2x80x9cIxe2x80x9d being the intensity of each of the other peaks.
As will be understood by those skilled in the art the determination of the parameter 2xcex8 is subject to both human and mechanical error, which in combination can impose an uncertainty of about xc2x10.4xc2x0 on each reported value of 2xcex8. This uncertainty is, of course, also manifested in the reported values of the d-spacings, which are calculated from the 2xcex8 values. This imprecision is general throughout the art and is not sufficient to preclude the differentiation of the present crystalline materials from each other and from the compositions of the prior art. In some of the x-ray patterns reported, the relative intensities of the d-spacings are indicated by the notations vs, s, m, and w which represent very strong, strong, medium, and weak, respectively. In terms of 100xc3x97I/Io, the above designations are defined as
w=0-15;m=15-60:s=60-80 and vs=80-100
In certain instances the purity of a synthesized product may be assessed with reference to its x-ray powder diffraction pattern. Thus, for example, if a sample is stated to be pure, it is intended only that the x-ray pattern of the sample is free of lines attributable to crystalline impurities, not that there are no amorphous materials present.